Process of making metal strips and sheets from waste metal



W. C. JENKIN July 20, 1965 PROCESS OF MAKING METAL STRIPS AND SHEETSFROM WASTE METAL Filed Jan. 14, 1963 mvwfi v5.6 www \bqw INVENTOR. vW/LL/AM- C. JEN/(IN United States Patent PROCESS OF MAKING METAL STRIPSAND SHEETS FROM WASTE METAL William C. Jeukin, Dayton, Ohio, assignor toThe Cornmonwealth Engineering Company of Ohio, Dayton, Ohio Filed Jan.14, 1%3, Ser. No. 251,336

4 Claims. (Cl. 75-62) This invention relates to the making of metalstrips and the like of substantially pure metal, and more particularlyto the making of such metal strips by gas plating of metal onto asubstrate surface from which the metal is then stripped or removed.

Pure metal sheets and strips are useful for many purposes, e.g. aswrapping material, clad metal layers, decorative material, etc.Electrolytic processes for producing relatively pure metal deposits aredifiicult to practice, and require expensive and complicated equipment.Furthermore, in many instances electroplated metals are quiteunsuitable.

The invention contemplates the provision of a novel process forproducing relatively thin sheet and strip material of substantially puremetal, and without the use of electrolyte solutions of such metal. Thisis achieved by passing carbon monoxide over a mass of metal freed ofoxide and while maintained at a relatively high temperature, that issuch as will cause the formation of a metal carbonyl vapor. Theresultant metal carbonyl vapors are then passed to a deposition point orsubstrate, the surface of which has been preheated to permit thedeposited metal to be readily stripped or peeled therefrom.

In practice of the invention the metal which is subjected to the carbonmonoxide flow is first cleaned as by mechanically brushing or chemicallycleaning to present a clean metal surface free of oxide. While othersolid materials may be present it is preferable to provide a metalsurface as chemically and mechanically pure as possible, as this makesfor a more rapid procedure.

A metal mass, such as in the form of turnings or shavings, is heated ata temperature of about 500 F. and above, depending upon the metal beingreacted, and while thus heated carbon monoxide is brought in contacttherewith. The metal mass which is heated and contacted with carbonmonoxide may be a solid powder, or metal mesh, it being generallypreferable to provide for good contact of the carbon monoxide over :alarge area of the metal. Metal turnings or filing-s serve this purposeas well as they may be readily positioned in random fashion to provideintimate gas contact therewith to thereby enhance the gas plating rate.Metal wire, closely bunched, provides a similar good contact for thecarbon monoxide.

Carbon monoxide is attainable in cylinders commercially, and may beused. A more economical use, however, is effected by reclaiming andusing the carbon monoxide as exhausted from the gas plating chamber.

The invention will be more fully understood by reference to thefollowing detailed description and accompanying drawings wherein FIGURE1 is a view illustrating an apparatus arrangement useful in the practiceof the invention; and

FIGURE 2 is a view of a pure metal sheet produced in accordance with theinvention.

Referring now to the drawing, the numeral in FIG- URE 1 designates a gasplating chamber having an inlet 11 and an outlet 12. An endless belt 14is arranged to be moved through the gas plating chamber. A heater 16 isutilized to heat the endless belt as it is moved through the platingchamber. The endless belt preferably is made of stainless steel and ispretreated in chamber 18 to coat the belt with metal release materialsuch as a metal stearate, for example aluminum stearate or the like.

Metal carbnoyl is introduced into the plating chamber 10 and caused todecompose to deposit metal on the precoated endless belt 14. Afterdepositing the thin coating of metal uniformly over the surface of thebelt, the metal deposit is stripped away from the belt as at 20, andstored on the roll 21.

The metal may be recovered as a thin self-supporting sheet, such asindicated at 22, on the drawings, or be deposited onto a substratesurface.

For economical reasons, the metal plating gas is preferably prepared insitu during carrying out of the process, and making use of scrap orwaste metal as a starting material. The Waste or scrap metal ischemically cleaned of oxides and foreign matter, and then reacted whileheated with carbon monoxide to produce the gaseous metal carbonyl, thelatter being circulated by conventional means such as a fan, through thegas plating chamber from the metal carbonyl generator as indicated bythe arrows in the drawing. During the process metal bearing gas isthermally decomposed to deposit pure metal. The waste gaseous remainderincluding metal carbonyl, which is undecomposed is recirculated backthrough the generator and returned with newly generated metal carbonyl.As an inert carrier gas for facilitating circulation of the plating gas,there may be introduced gases such as helium, argon, carbon dioxide, andthe like.

While the prior art discloses the use of nickel carbonyl in theproduction of nickel metal coatings, and technical applications ofcopper carbonyl has been described, for example, in the Italianpublication Chimica (Milan) No. 7, July 1952, pages 284 and 285, it hasnot been heretofore known to produce these metals in the form of sheets,endless strips and the like starting with the impure metals.

The following examples are illustrative of the inven- -tion and how thepure metal may be recovered.

EXAMPLE 1 Copper metal strip A mass of copper scrap mesh-like wastecuttings is washed with nitric acid (1 part concentrated nitric acid in3 parts water by volume), and washed with clean Water. The resultantcleaned copper is transferred to a gas plating chamber and subjected toa flow of carbon monoxide while the copper mass is heated toapproximately or above. During heating after cleaning the waste copper,the same is kept covered with inert gas such as nitrogen or carbondioxide prior to passing carbon monoxide thereover. This preventsreoxidation of the chemically clean copper. Copper carbonyl gas which isproduced during the reaction is conveyed to the gas plating chamber, asillustrated in the drawings, and brought in contact with the surface ofthe endless belt moving through the chamber.

The surface of the belt is maintained at about 800 F. to cause the metalbearing gas to decompose and deposit copper metal on the belt surfacefrom which the copper metal deposit is stripped away.

EXAMPLE 2 Nickel metal strip A mass of nickel powder or fine turnings istreated with cleaning acid as in Example 1, and the resultant cleannickel heated to a temperature of 150 F. Carbon monoxide gas is thencirculated in contact with the heated metal. The pressure of thecontinuing flow of carbon monoxide impels the gas formed by the reactionof the nickel and the carbon monoxide towards the gas plating chamber,such as shown at it) in the drawing.

The metal bearing gas formed by contact of the carbon monoxide with theheated nickel metal is passed into contact with the precoated or treatedendless belt surface 3 and the nickel carbonyl decomposed at 800 F. todeposit thereover a thin film of nickel. Tests at the exhaust conduithave indicated that decomposition is substantially complete, no nickelbeing found in the exhaust. The film of nickel deposited on the belt isthen stripped therefrom and the cycle repeated.

a The invention provides a new and commercially practical method ofrecovering copper, nickel and the like metals from their scrap orsecondary metal form. The process broadly consists in converting thescrap or waste metal into a gaseous thermally decomposable compound ofthe metal and then depositing the metal onto a substrate surface fromwhich it can be readily stripped by heating and decomposing the heatdecomposable metal compound to cause the metal to be deposited on thesubstrate surface.

A suitable composition for coating the surface of the endless belt 14-,and such as illustrated in the drawings 25, consists in parts by weightof 100 parts petroleum naphtha (boiling range l50325 C.) and aluminumstearate 20 parts. Other metal fatty acid salts may be used in place ofaluminum stearate, for example magnesium palmitate.

Where desired, the gas plating may be carried out under sub-atmosphericpressure conditions, e.g. 1 mm. Hg. The temperature necessary to effectthe thermal decomposition of the metal carbonyl will vary depending uponthe particular metal compound used.

It will be understood that the foregoing description of the inventionmay be changed or modified to adapt it to dififerent metals andconditions as to temperature of decomposition, etc., and such obviousmodifications withinthe skill of the art is comprehended to fall withinthe scope of the invention as defined by the claims.

What is claimed is:

1. A process of recovering relatively pure metal from waste metal whichcomprises chemically cleaning said waste metal, subjecting the resultantclean metal to heat while protected from oxidation to the action ofcarbon monoxide to produce metal carbonyl, thereafter bringing the metalcarbonyl into contact with a heated endless belt waste copper metalwhich comprises chemically cleaning said waste copper metal, subjectingthe resultant clean metal to heat while protected from oxidation to theaction of carbon monoxide to produce copper carbonyl, thereafterbringing the copper carbonyl into contact with a. heated substratesurface coated with metal stearate and from which copper metal isstrippable and thermally decomposing the copper carbonyl to depositcopper metal onto said substrate, and then stripping the copper metaldeposit from the substrate surface.

3. A process of recovering relatively pure nickel from waste nickelmetal which comprises chemically cleaning said waste nickel metal,subjecting the resultant clean metal to heat while protected fromoxidation to the action of carbon monoxide to produce nickel carbonyl,-thereafter bringing. the nickel carbonyl into contact with a heatedsubstrate surface coated with. metal stearate and from which nickelmetal is strippable and thermally decomposing the nickel carbonyl todeposit nickel metal onto said substrate, and then stripping the nickelmetal deposit from the substrate surface.

4. A process of recovering relatively pure metal from waste metal whichcomprises chemically cleaning said Waste metal, subjecting the resultantclean metal to heat while protected from oxidation to the action ofcarbon monoxide to produce metal carbonyl, thereafter bringing the metalcarbonyl into contact with a heated endless belt substrate surfacecoated with metal stearate and from which metal is strippable andthermally decomposing the meal'carbonyl to deposit metal onto saidsubstrate, and then stripping the metal deposit from the substratesurface.

References Cited by the Examiner UNITED STATES PATENTS 2,159,412 5/39Wallis 22-57.4- 2,378,053 6/45 Wallis et a1. 22-57.4 2,612,440 9/52Altmann .56 2,685,121 8/54- Davis 2917 2,701,901 2/55 Pawlyk 22-57.4.2,981,128 4/61 Flemming -60 3,042,558 7/62 Kllble 207-10 BENJAMINHENKIN, Primary Examiner.

RICHARD N. EANES, Examiner.

1. A PROCESS OF RECOVERING RELATIVELY PURE METAL FROM WASTE METAL WHICHCOMPRISES CHEMICALLY CLEANING SAID WASTE METAL, SUBJECTING THE RESULTANTCLEAN METATO TO HEAT WHILE PROTECTED FROM OXIDATION TO THE ACTION OFCARBON MONOXIDE TO PRODUCE METAL CARBONYL, THERAFTER BRINGING THE METALCARBONYL INTO CONTACT WITH A HEATED ENDLESS BELT SUBSTRATE SURFACE FROMWHICH METAL IS STRIPPABLE AND THERMALLY DECOMPOSING THE METAL CARBONYLTO DEPOSIT METAL